Yellow-flowered Plants Research Articles

Taxonomic Reinstatement of the Endemic Chinese Species Iris thoroldii (Iridaceae) from I. potaninii and Reassessment of I. zhaoana.

Iris thoroldii is a perennial herbaceous plant with yellow, blue, or purple flowers. The species is native to the Tibetan Plateau and adjacent areas. In the literature and databases, I. thoroldii has long been treated in synonymy with I. potaninii. Currently, yellow-flowered plants of I. thoroldii are considered I. potanii, and blue-flowered plants are considered I. zhaoana, a replacement name for I. potaninii var. ionantha. This study aimed to clarify the taxonomic identity of I. thoroldii. A critical examination of original material, herbarium specimens, images of living plants, and the literature has shown I. thoroldii to be different from I. potaninii in some previously neglected macromorphological traits and to be conspecific with I. zhaoana. Thus, I. thoroldii is removed here from the synonymy of I. potaninii and accepted as a distinct species. This is endemic to China (central Gansu, Qinghai, and northwestern Sichuan provinces, and also Xinjiang Uygur and Tibet autonomous regions) and reaches the highest elevations compared with all other species in the genus Iris s.l. A revised taxonomy of I. thoroldii is provided, and two color forms, often co-occurring, are accepted: the autonymic yellow-flowered form (including a new synonym I. tigridia var. flavescens for which a lectotype was designated) and a form with blue or purple colors is proposed here, I. thoroldii f. ionantha. In addition, images of type specimens and detailed photographs of living plants for easy identification, along with the list of specimens of I. thoroldii that were examined, and also, comments on its distribution and habitats are provided.

Resolving the Puzzle of Iris maackii (Iridaceae): A Morphological Insight into Its Taxonomy.

Since the early 20th century, Iris maackii (Iridaceae) has been considered a synonym of I. laevigata, a synonym of I. pseudacorus, or an accepted species. The current concept of I. maackii in the literature and databases is often applied to yellow-flowered plants with prominently veined rosette leaves, which are diagnostic features of I. pseudacorus growing in Northeast Asia. Therefore, the objective was to clarify the taxonomic identity of I. maackii. This study is based on a critical examination of the literature, on the observed morphological characters in the holotype of I. maackii, and on a morphological comparison of I. maackii with living plants of I. laevigata and I. pseudacorus. Additionally, a morphometric comparison of the seed characters was carried out to clarify the morphological distinction among I. maackii, I. laevigata, and I. pseudacorus. A careful study demonstrated that the rosette leaf texture and the morphology of the flowering stem, fruit, and seeds of I. maackii are identical to or within the variation range of I. laevigata. Thus, I. maackii is morphologically non-distinct from I. laevigata and should be recognized as a taxonomic synonym of the latter. An image of the holotype of I. maackii is provided along with detailed illustrations of I. laevigata and I. pseudacorus.

Production of yellow-flowered gentian plants by genetic engineering of betaxanthin pigments.

Genetic engineering of flower color provides biotechnological products such as blue carnations or roses by accumulating delphinidin-based anthocyanins not naturally existing in these plant species. Betalains are another class of pigments that in plants are only synthesized in the order Caryophyllales. Although they have been engineered in several plant species, especially red-violet betacyanins, the yellow betaxanthins have yet to be engineered in ornamental plants. We attempted to produce yellow-flowered gentians by genetic engineering of betaxanthin pigments. First, white-flowered gentian lines were produced by knocking out the dihydroflavonol 4-reductase (DFR) gene using CRISPR/Cas9-mediated genome editing. Beta vulgaris BvCYP76AD6 and Mirabilis jalapa MjDOD, driven by gentian petal-specific promoters, flavonoid 3',5'-hydroxylase (F3'5'H) and anthocyanin 5,3'-aromatic acyltransferase (AT), respectively, were transformed into the above DFR-knockout white-flowered line; the resultant gentian plants had vivid yellow flowers. Expression analysis and pigment analysis revealed petal-specific expression and accumulation of seven known betaxanthins in their petals to c. 0.06-0.08 μmol g FW-1 . Genetic engineering of vivid yellow-flowered plants can be achieved by combining genome editing and a suitable expression of betaxanthin-biosynthetic genes in ornamental plants.

A field experiment characterizing variable detection rates during plant surveys.

Surveys aimed at finding threatened and invasive species can be challenging due to individual rarity and low and variable individual detection rates. Detection rate in plant surveys typically varies due to differences among observers, among the individual plants being surveyed (targets), and across background environments. Interactions among these 3 components may occur but are rarely estimated due to limited replication and control during data collection. We conducted an experiment to investigate sources of variation in detection of 2 Pilosella species that are invasive and sparsely distributed in the Alpine National Park, Australia. These species are superficially similar in appearance to other yellow‐flowered plants occurring in this landscape. We controlled the presence and color of flowers on target Pilosella plants and controlled their placement in plots, which were selected for their variation in cover of non‐target yellow flowers and dominant vegetation type. Observers mimicked Pilosella surveys in the plots and reported 1 categorical and 4 quantitative indicators of their survey experience level. We applied survival analysis to detection data to model the influence of both controlled and uncontrolled variables on detection rate. Orange‐ and yellow‐flowering Pilosella in grass‐ and heath‐dominated vegetation were detected at a higher rate than nonflowering Pilosella. However, this detection gain diminished as the cover of other co‐occurring yellow‐flowering species increased. Recent experience with Pilosella surveys improved detection rate. Detection experiments are a direct and accessible means of understanding detection processes and interpreting survey data for threatened and invasive species. Our detection findings have been used for survey planning and can inform progress toward eradication. Interaction of target and background characteristics determined detection rate, which enhanced predictions in the Pilosella eradication program and demonstrated the difficulty of transferring detection findings into untested environments.

Flower colour divergence is associated with post-fire regeneration dimorphism in the fynbos heath Erica coccinea subsp. coccinea (Ericaceae)

The South African Cape fynbos heath Erica coccinea subsp. coccinea is polymorphic for post-fire regeneration mode (seeder/resprouter), flower colour (red/yellow), flowering time (summer-autumn/winter-spring), as well as anther size. These polymorphisms tend to occur between, rather than within, populations. Here, we aimed to understand flower colour divergence in this fynbos heath species and its association with post-fire regeneration. We tested for an association between these polymorphisms. We also examined whether yellow-flowered plants lacked anthocyanins and whether the lack of anthocyanins affected the concentration of other flavonoids, both in flowers and shoots. We found a strong association between flower colour, regeneration mode and flowering phenology. We also detected larger anthers and larger pollen in yellow- than in red-flowered plants, consistently for both resprouter and seeder regeneration strategies. Finally, we ascertained that being yellow-flowered is associated with loss in the capacity of synthesizing anthocyanins in both the flower and in the vegetative tissue. Considering that pollinator availability or preferences do probably not constitute a selection pressure, we propose that both enhanced reproductive success of anthocyaninless, yellow-flowered plants and the avoidance of likely negative pleiotropic effects (early senescence) in seeders would be key to understanding the flower colour divergence in E. coccinea subsp. coccinea.

Floral damage induces resistance to florivory in Impatiens capensis

Many plants produce defense chemicals that are induced in response to damage. In spite of the tight links between floral tissue and plant reproduction, very little is known about whether floral defenses are induced in response to floral damage. We manipulated Impatiens capensis flowers to determine whether floral damage reduces subsequent florivory, whether it induces anthocyanins or condensed tannins in floral tissues, and whether responses are localized or systemic. We damaged one flower per plant at one of three damage levels (0, 30, or 60 % tissue removal), collected subsequent flowers at set time intervals and branch locations, and measured whole-plant florivory for 3 weeks following damage. We also observed a flower color polymorphism and analyzed responses separately for red- and yellow-flowered plants. Moderate damage to a single flower reduced subsequent whole-plant florivory, but heavy damage did not. Moderate damage to a focal flower also increased anthocyanins in subsequent flowers on the same branch of red-flowered plants, but decreased anthocyanins on parallel-branch flowers of yellow-flowered plants. Damage did not affect floral tannins. Because the reduction in florivory was systemic and induced anthocyanins were not consistently induced systemically, there may be other secondary compounds not measured in this study that were systemically induced, or effects of visual or olfactory cues of damage itself that reduced subsequent florivory. This is the first study demonstrating that damage to a single flower can reduce subsequent whole-plant florivory in the field, indicating that initial damage can have cascading effects on subsequent interactions.

Taxonomy and evolution of the Convolvulus sabatius complex (Convolvulaceae)

A revision of the Convolvulus sabatius complex is presented and five taxa are now recognised. Convolvulus valentinus is re-circumscribed to comprise only blue-flowered individuals. Yellow-flowered plants previously referred to this species are transferred to C. supinus where they are recognised as a distinct variety: C. supinus var. melliflorus, comb nov. Variation in intensity of flower colour, pubescence and leaf shape among blue-flowered C. valentinus is highly variable within populations and in contrast to earlier treatments, no infraspecific taxa based on these traits are recognised. Despite suggestions to the contrary, the delimitation of the cultivated ornamental C. sabatius and its two subspecies is unproblematic. Molecular data from the chloroplast trnH-psbA region support the recircumscription of C. supinus and C. valentinus and highlight the genetic distinctiveness of a disjunct Iberian population of the latter that merits further investigation.

Environment and pollinator‐mediated selection on parapatric floral races of Mimulus aurantiacus

We tested whether selection by pollinators could explain the parapatric distribution of coastal red- and inland yellow-flowered races of Mimulus aurantiacus (Phrymaceae) by examining visitation to natural and experimental populations. As a first step in evaluating whether indirect selection might explain floral divergence, we also tested for local adaptation in early life stages using a reciprocal transplant experiment. Hummingbirds visited flowers of each race at similar rates in natural populations but showed strong (>95%) preference for red flowers in all habitats in experimental arrays. Hawkmoths demonstrated nearly exclusive (>99% of visits) preference for yellow flowers and only visited in inland regions. Strong preferences for alternative floral forms support a direct role for pollinators in floral divergence. Despite these preferences, measures of plant performance across environments showed that red-flowered plants consistently survived better, grew larger and received more overall pollinator visits than yellow-flowered plants. Unmeasured components of fitness may favour the yellow race in inland habitats. Alternatively, we document a marked recent increase in inland hummingbird density that may have caused a change in the selective environment, favouring the eastward advance of red-flowered plants.

Bumblebee Foraging Responses to Variation in Floral Scent and Color in Snapdragons (Antirrhinum: Scrophulariaceae)

We examined the roles of floral scent and color in attracting bumblebees (Bombus spp.) to snapdragon flowers (Antirrhinum, Sonnet cultivar). Corolla color differences covaried with differences in floral scent emissions in two inbred lines of snapdragon. White-flowered plants emitted methyl cinnamate, a scent compound not produced by yellow flowered plants, but lacked methyl benzoate, one of the major floral volatiles of the yellow-flowered line. Qualitative scent differences between the two lines were eliminated by applying the complementary scent compounds to filter paper wicks placed within the corollas. Laboratory analyses were performed using gas chromatography-mass spectrometry to verify appropriate modification of floral scents by this method. Two randomized arrays of control and scent-augmented flowers were visited by freely-foraging bumblebees in subalpine meadows in Colorado. Overall, yellow-flowered plants received more pollinator visits and had more flowers foraged per plant visit than did white-flowered plants. The addition of sweet-smelling methyl benzoate or spicy methyl cinnamate neither stimulated nor deterred bumblebee visits to either flower color.

Inheritance of yellow-flowered characteristic and yellow pigments in diploid cyclamen ( Cyclamen persicum Mill.) cultivars

The mode of inheritance of the yellow-flowered phenotype of yellow-flowered cyclamen was investigated. All F 1 progenies obtained by reciprocal crosses between yellow- and white-flowered cultivars were white-flowered and did not contain chalcone, the main pigment of yellow-flowered cyclamen. The segregation ratio of flower colors in most of F 2 and BC 1 progenies fitted the expected Mendelian ratio, showing that the yellow-flowered phenotype was controlled by a single recessive gene. The petals of all yellow-flowered plants in F 2 and BC 1 progenies contained chalcone. It is suggested that a single recessive gene causes the lack or defectiveness of chalcone-flavanone isomerase and determines the yellow-flowered phenotype.

Chromosomal and genic structure of Brassicoraphanus related to seed fertility and the presentation of an instance of improvement of its fertility

In order to elucidate the mechanism of low fertility of Brassicoraphanus, i.e., amphidiploids between Brassica japonica Sieb. and Raphanus sativus L., the chromosome number of 253 plants was studied during the 3rd–9th generations for their seed fertility. Meiotic irregularity showed no connection with degree of sterility. Brassicoraphanus consisted of euploids (2n=38), hyperploids (2n=39–43) and hypoploids (2n=34–37) with white or yellow flowers. The number of plants was highest in euploids and became lower as the chromosome number diverged from the euploid number. Further, seed fertility was highest and the range of its variation widest in euploids. The seed fertility of aneuploids became lower and its variation narrower in proportion to the number of chromosomes additional to or missing from the euploid number. Yellow-flowered plants were superior in seed fertility to white-flowered plants. Seed fertility of plants is primarily affected by their chromosome numbers and secondarily modified by genic effects. As a whole, seed fertility of Brassicoraphanus increased gradually and its variation widened with the advance of generations. This was explained mainly by the increase of balanced combinations of genes.

Taxonomy of glandular wild alfalfa (Medicago sativa)

Yellow-flowered plants of Medicago sativa L. sensu lato with coiled pods covered with glandular trichomes are treated as M. sativa subsp. glomerata (Balbis) Rouy, and those with yellow flowers and uncoiled glandular pods as M. sativa subsp. falcata (L.) Arcangeli var. viscosa (Reichenb.) Posp. Synonymy of these and common hybrid forms is given.

Morphological differentiation in Medicago sativa s.l. in relation to ploidy

A study was undertaken of the yellow-flowered and violet-flowered diploid (2n = 2x = 16) and tetraploid phases of Medicago sativa s.l., excluding the widespread hybrid derivatives between the two flower-colour variants. It was found that diploid and tetraploid yellow-flowered plants (M. sativa ssp. falcata collectively) exhibit substantially overlapping morphological variation. However, among violet-flowered plants, the examined samples of diploids (M. sativa ssp. caerulea) and tetraploids (M. sativa ssp. sativa) proved to be completely separable by discriminant analysis. Most characters of ssp. sativa are quantitatively greater than those of ssp. caerulea. This and other considerations are consistent with an autopolyploid origin.

Morphologic and Cytotaxonomic Evaluation of Lomatium tuberosum (Apiaceae)

Lomatium tuberosum Hoover, a south-central Washington endemic, has been considered to be closely related to three other normally purple-flowered lomatiums:L. columbianum, L. cuspidatum, andL. minus. Recent morphologic studies confirm the close phenetic relationship of these four species. Chromosome counts from a purple-flowered population in the eastern range ofL. tuberosum indicaten=11, the same chromosome number earlier determined with yellow-flowered plants from the type locality.

Evaluation of potential genetic marker traits and estimation of outcrossing rate in Stylosanthes guianensis

The inheritance of flower, seed testa, and hypocotyl colour, and growth habit were studied in the F2 generation of biparental crosses between Stylosanthes guianensis accessions exhibiting contrasting phenotypes. Segregation ratios for flower colour in seven crosses and the pooled ratio supported a conclusion of single-gene inheritance, with yellow dominant to white. The data on seed colour (purple v. brown) gave inconsistent results in the two crosses evaluated. Neither red v. white hypocotyl colour nor normal v. dwarf growth habit appeared to be inherited monogenically, since a range of intermediate phenotypes was observed in the F2 populations examined. The open-pollinated progenies of 12 homozygous recessive (white-flowered) individuals within one F2 population contained yellow-flowered plants attributed to outcrossing. Overall outcrossing rate ( � s.e.) was estimated as 0.138�0.021. The proportion of yellow-flowered outcrosses in these 12 progenies was related to the number of yellow-flowered individuals adjacent to the F2 parent, indicating that pollen movement was limited within the F2 plot. Based on these findings a practical, recurrent population improvement scheme for S. guianensis is proposed.

The stabilization of chromosome numbers and the maintenance of euploidy in Brassicoraphanus

To examine whether chromosome numbers of Brassicoraphanus (amphidiploids between Brassica japonica Sieb. and Raphanus sativus L.) are stable or not, the following four items were studied with some plants during the 2nd–11th generations: (1) chromosome numbers of open-pollinated progenies from eu-, hyper-, and hypoploids, (2) chromosome distribution at metaphase II in these plants, (3) frequency of euploids in relation to flower colour and generation, (4) seed fertility in eu-and aneuploids in relation to flower colour. In early generations, hyper-and hypoploids were frequently produced from euploids. In later generations, however, the chromosome number became less unstable. In euploids (2n=38), chromosome numbers at metaphase II showed some variation, and the mean frequency of the euploid chromosome number (n=19) was approximately 78%. This value was almost the same in white-and yellow-flowered plants through early and late generations. Nevertheless, yellow-flowered plants tended to produce euploids more frequently than did white-flowered ones. It is assumed that the difference in euploid productivity between yellow-and white-flowered plants is due to the difference in seed fertility between them. The progeny of each hypoploid showed higher chromosome numbers than their parents. The progeny of each hyperploid showed lower chromosome numbers than their parents: they were approaching to euploidy. This phenomenon, together with higher fertility of euploids and lower fertility of aneuploids, will favor the maintenance of euploidy of this strain.

Variation and Taxonomy of Aesculus pavia L. (Hippocastanaceae) in Texas

The status of Aesculus pavia var. flavescens, a set of yellow-flowered populations endemic to the Edwards Plateau of central Texas, was evaluated on the basis of comparative morphology, geography, flowering phenology, and pollination ecology. Plants of typical A. pavia have red, tubular flowers with exserted stamens and are effectively pollinated by ruby-throated hummingbirds. Plants of var. flavescens have yellow, campanulate flowers with included stamens that can be pollinated effectively by large bees. These ethological reproductive isolating mechanisms are further augmented by a difference in flowering time between the two sets of populations and by geographical restriction of the yellow-flowered plants to localities on the Edwards Plateau. The yellow and red-flowered plants constitute two morphologically distinct groups, despite evidence of limited introgression in counties along the Balcones Escarpment. A yellow-flowered plant discovered in coastal east Texas may indicate the mechanism by which var. flavescens originated, but this plant is much more closely comparable to typical red-flowered var. pavia than to the yellow-flowered plants on the Edwards Plateau. An evolutionary history of section Pavia of Aesculus is presented, and it is concluded that the yellow-flowered plants of central Texas are best regarded as a taxonomic variety.

The mechanism of increased seed fertility accompanied with the change of flower colour in Brassicoraphanus

In Brassicoraphanus (amphidiploids between Brassica japonica Sieb. and Raphanus sativus L.), yellow-flowered plants that occurred among originally white-flowered plants showed an increased seed fertility. It is assumed that the gene Y (yellow-flower gene) from Brassica and the gene W (white-flower gene) from Raphanus are located at corresponding loci of only partially homologous chromosomes. W is dominant (epistatic) over Y. The normal white-flowered plants have the genotype YYWW. A YYYW-plant was found, which is assumed to have arisen through crossing-over following multivalent formation. In the progeny of this plant, yellow-flowered plants (YYYY) as well as white-flowered plants (YYWW, YYYW) appeared. The gene for flower colour is closely linked to a gene which controls the development of embryos (or endosperm). This gene promotes the development of embryos in homozygous condition. Therefore, the embryo having only the yellow-flower gene can develop more easily into viable seed than the embryo having the white-flower gene. It is also possible that the sterility of white-flowered plants is caused by a discordance between the cytoplasm of Brassica and W (or genes linked to W) of Raphanus.

The increase of seed fertility of Brassicoraphanus through cytological irregularity

Amphidiploids (Brassicoraphanus) were produced by means of colchicine treatment of F1 hybrids between Brassica japonica Sieb. and Raphanus sativus L. The cytology of the amphidiploids was studied from F1 to F3 generations. Some plants had the euploid chromosome number 2n=38, whereas others had the aneuploid number 2n=37. One or two of either quadrivalents or trivalents, as well as some univalents, were seen in most of the plants examined. All the plants showed a low seed fertility. In F3 generation there arose some yellow-flowered plants, all of which showed a higher seed fertility than normal white-flowered plants. It is postulated that the change of flower colour might originate in the segmental exchange of only partially homologous chromosomes following multivalent formation. A gene causing white flower colour was perhaps closely linked to a gene causing sterility, and both genes were probably excluded together through the segmental exchange of the chromosomes. Therefore, it can be said that the increase of fertility was induced by cytological irregularity.

Variation in the spectral qualities of flowers in the Nymphoides indica complex (Menyanthaceae) and its possible adaptive significance

The Nymphoides indica complex is polymorphic in the spectral qualities of its flowers. Flowers of the circumtropical white-flowered race absorb ultraviolet light strongly. Flowers of yellow-flowered South African plants reflect almost uniformly, but those of yellow-flowered plants from the West Indies absorb more strongly in the center and reflect from the remaining portion of the petals. The evolution of these contrasting patterns is considered to represent an increasing specialization of pollinator–flower relationships because of the effect these patterns have in directing pollinating insects to the flowers and to the reproductive organs of the flower.